Process of impregnating cellulosic materials with copper in chemically bound relation with the cellulose



PROCESS OF IMPREGNATING CELLULOSIC MA- TERIALS WITH COPPER IN CHEMICALLY BOUND RELATION WITH THE CELLULOSE Robert Roger Bottoms, Crestwood, Ky., assignor to National Cylinder Gas Company, Chicago, 1111., a corporation of Delaware No Drawing. Application February 16, 1954, Serial No. 410,719

30 Claims. (Cl. 117-59) This invention relates to the preservation of cellulosic materials against deterioration and attack from organic, i. e. biological, agents of decay. More particularly, it relates to cellulosic compositions which possess increased immunity against organic agents of decay and to a process for increasing such immunity of cellulosic materials.

The preservation of cellulosic materials has been the subject of considerable study. Forms of protection have been proposed or used with respect to one or more of the types of cellulosic materials but all such forms of protection, so far as is now known, either achieve the protection at the expense of some property or properties of the cellulosic material or are unwieldy and impractical to use or are rendered impotent by weathering or by the leaching efiect of solevnts. None, so far as is known, involves a chemical union of the preserving material with the cellulose in a manner which resists removal by a specific solvent or reagent for the particular preservative agent incorporated in the cellulose.

For example, impregnation of wood with creosote and like substances is widely practiced and is eifective where 9 there is no objection to the color or odor of the treating material or the treated product, but this method cannot be used where it is desired to employ the wood in structures to be painted or where the color and odor of the treated wood is objectionable. Moreover, such treatment is not applicable to cellulosic products other than wood as for example, cotton, cotton fabrics and paper without serious or total impairment of their utility. In addition, compounds of copper and arsenic have been employed by depositing a relatively insoluble compound of copper or arsenic in or among cellulosic fibers. Such processes have depended upon the introduction of materials into or on the cellulose fibers and then fixing or rendering them water-insoluble. Various methods of accomplishing this have been proposed. Patent No. 2,194,827, March 26, 1940) to impregnate wood with a soluble metal salt and to insolubilize the metal by reacting the salt with a compound containing an insolubilizing anion such as ammonium phosphate or sodium carbonate in aqueous ammonia. Patent No. 1,846,185, February 23, 1932, proposes insolubilizing a Water soluble copper salt with which mulch paper has been impregnated by reacting that salt with a copper precipitant, as for example caustic soda or sodium carbonate, which precipitates the copper as the hydroxide or the carbonate. It has also been proposed to impregnate textile materials with a Water soluble copper salt and to precipitate the copper as the copper salt of an alkylene succinic acid, which is insoluble in water, or to apply this insoluble copper salt to textiles in the form of an aqueous dispersion (see Patent No. 2,381,852, August 7, 1945). it has also been proposed to treat textile materials by coating the fibers with a water insoluble copper salt as for example copper naphthenate. The water insoluble copper compounds in products resulting from processes of these types are merely physically disposed on and in the cellulose fibers and are removed by physical or chemical It has thus been proposed (see nited States batent ice action as for example reacting or leaching with a solvent or reagent for copper, as for example, ammonia or sequestering or chelating agents which have strong afiinity for copper, such as synthetic polyamino polycarboxylic acids and their salts of which the sodium salt of ethylene diamine-tetraacetic acid is an example. No chemical combination of the copper with the cellulose molecules, resistant to such leaching, is found.

It is an object of this invention to provide a means for chemically binding preservative agent to the cellulose molecules by valence bonds which resist removal of the chemically bound preservative agent by physical or chemical means. It is a further object of this invention to provide means for uniting copper in chemically bound relation with cellulose molecules and to provide a cellulose composition containing copper chemically bound to the cellulose molecules of such composition.

A further object of the invention is to provide a coppercellulose complex wherein properties characteristic of cellulose are modified.

The products of this invention have marked immunity to agents of decay, as for example animal and plant organisms such as fungi, bacteria, insects, wood-borers, worms, other marine life, and especially cellulose destroying molds such as Chaetomz'um globosum and those bacteria and organisms associated with soil. Thus wood, cotton and regenerated cellulose as well as other cellulosic materials treated according to this invention exhibit strong immunity to agents of decay. V

The method of this invention fundamentally includes impregnating cellulosic material with copper formate and effecting chemical reaction of the thus-introduced copper formate to provide a reaction product of copper and cellulose, whereby a substantial portion of the retained copper is chemically combined with cellulose molecules. This chemical combination of copper and cellulose is accomplished by heating the impregnated cellulose to a temperature above about C. but below temperatures that are capable of deleteriously affecting the cellulosic material. In the chemical reaction of the copper impregnated cellulose, formic acid (or its decomposition products) is released. While the precise nature of the chemical combination of copper with cellulose molecules is not known, the fact of chemical combination has been demonstrated.

The impregnation of cellulosic material with copper formate may be accomplished in any convenient manner. For example, an aqueous solution containing dissolved cupric formate may be applied to the cellulosic material. A copper formate solution containing from 1 to 12% by weight cupric formate may be employed. I have found that solutions in the lower portion of this range are ordinarily adequate for purposes of the process and I generally prefer solutions containing from 1.5% to 4% cupric formate. Any suitable solvent for copper formate may be employed but for obvious reasons, I prefer water as the solvent. When aqueous solutions are employed, they may also contain minor amounts of organic liquids, preferably water miscible organic liquids such, for example, as ethyl alcohol, methyl alcohol and dioxane. it has also been found that small amounts of non-ionic wetting agents may be included to facilitate the impregnation. Particularly applicable are those types of wetting agents designed to be used in the presence of a high salt content at a low pH. Suitable wetting agents include saponin and its derivatives, condensation products of ethylene oxide with fatty substances and their derivatives, which are commercially obtainable as Advawet and lntral 222, 231 and 233, condensation products with ethylene oxide of phenolic compounds having side chains, which are commercially available as Triton. Other wetting agents and penetrants may be used. It will also be apparent that copper formate may be introduced into the cellulosic material by first impregnating that material with a soluble copper salt and treating the thus impregnated material with formic acid to form copper formate in situ. However, it is generally preferred to accomplish the introduction of copper formate into the celiulosic material by impregnation with a solution of copper formate. The impregnation may be carried out under conditions whereby the impregnated cellulose contains copper formate equivalent to a copper content of belt. con 0.01% and 2% based on the dry weight of the cellulose material.

In the case of wood, this pickup is governed by the conditions of the impregnation, as for example the conditions and extent of the vacuum pretreatment period and the pressure, temperature and time of the following impregnation. Conventional methods for impregnation of wood may be followed with due regard to attainment of the desired pickup of copper formate and its uniforn impregnation through the wood.

In the case of ccllulosic materials such as cotton, regenerated cellulose, jute and sisal and articles and fabrics containing them, the pickup of copper formate is governed by the retention of the copper formatc solution by the materials and by the concentration of the copper formate treating solution. In the case of such materials, the retention may conveniently be controlled by passing the impregnated material through rollers to give any desired attainable pickup. In practice, it is preferred to process impregnated cellulosic materials of these types to give a 50% to 80% pickup. A wet pickup of 70% is very satisfactory for cotton and regenerated cellulose fibers, filaments or fabrics. The impregnation may be suitably efiected by soaking the material in an aqueous solution of cupric formate or by applying suitable quantitles of cupric formate to the material as by spraying.

The step of heating the impregnated cellulosic material to effect chemical combination of copper and cellulose may be accomplished in any convenient manner. The heating step may be carried out in an autoclave in an atmosphere of steam under pressure suitable to attain the desired temperature, or it may be accomplished in air at atmospheric, reduced or increased pressure, or in an atmosphere of other gases as, for example, nitrogen or hydrogen at atmospheric, reduced or increased pressure. The upper limit of temperature to be employed in the heating step naturally depends somewhat on the particular cellulosic material being treated, it being desirable to avoid deleteriously high temperatures, but, in general, it may be specified that 200 C. is a limit which desirably is not exceeded and that the preferred temperature range for this phase of the treatment is between about 100 C. and 125 C. Temperatures higher than about 150 C. are usually unnecessary and may be avoided.

The duration of the heat treatment to etlect the desired chemical reactions resulting in chemical union of copper with cellulose is not critical and depends largely on the size, form and species of the cellulose material undergoing treatment. Ordinarily from ten minutes to about one hour is a satisfactory duration for the heating step, but it will be understood that in any case it is necessary that the material be heated for a time sufficient to insure it reaching a temperature of at least 100 C. throughout. It will also be understood that the duration of heating is somewhat dependent upon the manner in which the heat is applied. The heating at a suitable temperature should be continued until the characteristic green color imparted to the impregnated cellulosic material by the copper formate has changed to a tannish or olive color.

The effect of such treatment of cellulose materials is to provide a cellulose composition containing a coppercellulose reaction product or complex in which copper is chemically bound to cellulose molecules. The chemical combination of copper and cellulose is evidenced by differcnces in properties between the reaction product or copper-cellulose complex and uncombined copper and cellulose components. Properties of each component are decidedly modified in the chemical combination.

Modification of the copper component by reason of the chemical combination with cellulose is conveniently demonstrated by comparison of the solubility of that portion of the retained copper which is not chemically combined with cellulose to that portion of the retained copper which is so chemically combined. Of the retained copper resulting from treatment of cellulose according to this invention, that portion which is not bombincd with cellulose and which appears from X-ray diffraction studies to be present in the form of cuprous oxide is readily dissolved and removed in a short time from the cellulose by extraction with a reagent or solvent for copper as for example 4% aqueous solution of ammonia. Also, cxtrnction with such substances readily removes all of the copper from copper formate-impregnatcd cotton fabric that is merely air dried. Such extraction also results in total elimination from ccllulosic materials of copper compounds which have been deposited as water insoluble compounds such, for example, as copper oxide, copper hydroxide, copper alkylenc succinate, or copper naphthenatc. By contrast, the copper component of the copper-cellulose complex is not dissolved or removed by eXtrt-tction with aqueous solution or" ammonia, even though the extraction is carried out for a period of one hour to twenty-four hours.

Properties of the cellulose component of the copper cellulose complex are also modified. For example, the cellulose in the complex is not appreciably soluble in cupriethylene diamiue or cuprammonium. it l' lfi'i'fil. such cellulose is not readily hydrolyzable in mil al acid. nor does caustic afiect it in the manner characteristic of unmodified cellulose.

Moreover, X-ray diffraction stu..ies demonstrate the chemical combination. Cellulose, treated according to this invention, shows the pattern characteristic of cuprous oxide. However, X-ray diffraction studies of cellulosic material treated according to this irwcntion and then extracted or leached with 4% acgucous ammonia solution fail to SllOW the characteristic cuprous oxide put- I. l I! act that the tern or the pattern of copper dcspit the samples examined have been determined by chemical analysis to contain as much as 0.4% copper.

In the process and product of this invention, while a substantial portion of the copper which has been introduced as copper formate is converted into copper that is firmly bonded chemically to the cellulose molecules, i. c. resistant to treatment with, a 4% acqucous solution of ammonia for one hour, not all of the copper so introduced is ultimately found in such firmly bound form. In addition to that amount of the retained copper which is firmly bonded chemically to cellulose and is represented by the amount of residual copper determined by chemical analysis of a product which has been extracted for one hour with a 4% aqueous solution of ammonia, a substantial portion of the remainder of the retained copper which is removed by such extraction may also have been chemically bound to cellulose. If chemically bound, it is obviously less firmly bonded to cellulose molecules than the bound copper which survives this extraction or reaction, and is bound by forces or in a manner not capable of resisting the strong affinity which such solvents or reagents have for copper.

The proportion of retained copper which is firmly chemically bonded to cellulose molecules varies considerably with the particular type of cellulose treated. Generally speaking, the greater the proportion of amorphous cellulose to crystalline cellulose in a particular material the greater will be the proportion of retained copper in firmly bound form. The greatest advantage and most noticeable increases in immunity to the agents of decay will be noted in the treatment of those types of cellulose which contain substantial amounts of amorphous cellulose. These types include wood, regenerated cellulose -(e. g. viscose), cotton and, to a somewhat lesser degree, the hemi-celluloses, such as jute and sisal.

At any rate, all of the retained copper in the cellulose materials treated according to this invention appears to contribute to the immunity of the cellulose to cellulolytic agents. In some unexplained manner, the presence of the firmly chemically combined copper, apparently bound by cross-linking to adjacent cellulose polymer chains, potentiates the preservative properties of the loosely bound or unbound copper, at least a portion of which latter must be assumed, from X-ray difiraction studies, to be present as cuprous oxide. This po-tentiation is apparent from the fact that cotton fabric treated according to the process of this invention and containing 0.85% retained copper and which showed good mildew resistance was, after ball-milling for forty-eight hours, as vulnerable to mildew as untreated cotton. The ball-milling effectively separates the adjacent cellulose molecules thus destroying the firm cross-linked chemical combination of copper with cellulose and thus eliminating potentiation of the preservative effect of the uncombined or loosely combined retained copper by that firmly chemically combined with the cellulose.

Moreover, copper formate when employed according to this invention uniquely increases the immunity of cellulose to decay as compared with copper salts of homologously related organic acids. Thus, strips of cotton duck were treated respectively with copper formate according to this invention and with copper acetate and copper propionate under precisely the same conditions. After twelve weeks exposure in soil burial beds under identical conditions the strips treated with copper acetate and copper propionate showed no residual strength while a strip treated with copper formate showed a retention of 75% of its original strength.

It will be understood that the desirable amount of retained copper and copper firmly chemically bound to cellulose molecules may vary with the conditions which the treated material is designed to withstand. The agents of decay associated with soil appear to be the most active. Certain forms of marine organisms also have shown considerable potency as agents of deterioration and decay. Some other cellulose-destroying organisms such as C. globosum appear to be relatively easily inhibited. Moreover, the effect of any given agent of decay or combination of such agents is of course modified by factors of environment as for example light, temperature and moisture. Thus, there is difiiculty in prescribing definite values for the retained or the firmly combined copper content to be incorporated in any particular instance. In general, however, as has been stated, the retained copper content may be between 0.01% and 2%, based on dry weight of cellulosic material. Retained copper values in this range include between 0.005% and 0.8% of chemically combined copper, based on dry weight of cellulosic material. Retained copper values of from 0.1% to 1%, with corresponding values for firmly combined copper of 0.05% to 0.4% are ordinarily preferred. These are satisfactory potentiating amounts for many purposes. It will be understood that to withstand more rigorous deteriorating conditions, higher retained and firmly combined copper contents are more desirable and that to withstand action of the less potent deteriorative conditions lesser amounts may be adequate.

The efficacy of the treatment of cellulose according to this invention has been demonstrated by relatively rigorous exposures of treated material to various agents of decay along with untreated control samples of the same material. In the case of Wood, specimens of oak and tupelo gum wood in the form of pieces of l"'x 1" x 18" were treated according to this invention so that the wood contained 1% by weight of copper in the case of the oak and about 0.5% by weight of copper in the case of the tupelo gum. These specimens were then driven verti cally in the ground in swampy soil near Louisville, Kentucky, along with untreated specimens of the same woods in the same form and size. Each specimen was buried except for 1 /2 of its length. The site of this test was adjacent to an abandoned wooden structure which was infested with termites.

After twenty-one months, this series of tests was discontinued because the untreated tupelo gum wood specimens had been almost entirely consumed by decay or insects or both. The untreated oak specimens were in better condition, but these were partly consumed, and were weakened to a point that rendered the wood useless. The specimens of both species of Wood treated according to this invention were literally unaffected by the exposure. The treated tupelo gum wood specimens, when washed free of soil, showed absolutely no evidence of any decay or attack by insects. The oak specimens also showed a total absence of decay or attack by insects. The exposed, treated specimens of both species of wood were found to be sound throughout, and unaffected in strength.

In another series of tests, treated and untreated specimens of oak and yellow pine in the form of 2" X 4" and 2" x 2" sections some 2 feet in length were exposed in tropical soil near Barranquilla, Colombia. After approximately six months exposure, the untreated specimens were found to be largely consumed due to termite infestation, while the treated specimens of oak were wholly unattacked, and the treated specimens of pine showed only very slight indication of some attack, apparently by insects, at the extreme ends of the specimens, but were otherwise unaffected. The treated wood used in these tests was prepared in accordance with the present invention and contained slightly less than 1% of copper.

In the case of cotton, pieces of cotton duck were treated according to this invention, the heating step being carried out at C. to give a retained copper content of 1.04% on the weight of the cotton. A sample of the treated material was leached with 4% aqueous ammonia for one hour and by analysis it was determined there remained a copper content of 0.59% indicating the proportion of firmly bound copper to total copper. The treated, unleached cotton duck was subjected to twelve weeks exposure in a soil burial bed maintained under moisture and temperature conditions conductive to activity of the organisms contained in the soil. The untreated control strip of cotton duck and strips impregnated with copper acetate, copper propionate and heated to 125 C. and strips impregnated with copper naphthenate were similarly imbedded. After twelve weeks exposure in the soil burial beds, the following percentages of retained strength were determined: control strip-0%; strip treated according to this inventicn78%; strip similarly treated with copper acetate0%; strip similarly treated with copper propionate0%; strip upon which copper naphth'enate was deposited50%. Upon exposing similarly treated strips of cotton duck to the action of C. globosum, strips treated according to this invention and strips impregnated with copper naphtbenate did not decrease in strength by reason of action of the organisms nor allow any substantial growth whereas the control strips and the strips treated with copper acetate and copper propionate showed a large decrease in strength by reason of the action of the organism and appeared to support its growth. Similar results have been obtained on subjecting cellulose materials to the action of marine organisms in subtropical waters.

Treatment of cellulosic material according to this invention may result in small decreases in strength of the treated product as compared with untreated material. No appreciable change in strength has been noted in the case of wood. 'In the case of cotton fibers and fabrics and hemicellulosematerials, some decrease in strength may be encountered. However, any decreases in strength which have been noted are very small in comparison to the decrease in strength caused by action of agents of decal on untreated cellulosic materials or cellulosic materials treated with previously known preservatives.

Cellulose fibers or filaments treated according to this invention are suitable for employment in the manufacture of threads, yarns, fabrics and the like. Cellulosic fabrics treated according to this invention or constructed from fibers, filaments, threads or yarn so treated are suitable for general use and may be d ed without impairment of their resistance to organic agents of decay. Ordinary substantive dyes for cotton are generally not satisfactorily taken up by treated cotton, but dyes applicable to modified cellulose may be used. The treatment according to this invention is also applica ilc to dyed cellulosic fabrics. Moreover, ccllulosic materials treated according to this invention are neither primary irritants nor secondary sensitizers when in contact with human skin.

Decay resistant cellulose-base paper may also be prepared according to this invention. Wood chips may be treated according to this invention and then utilized in the manufacture of paper by any convenient process as for example the sulfate or the sulfite process. In any case, the retained copper, including that firmly chemically bound, remains in the pulp and a paper, resi tant to the agents of decay, results. Similar beneficial results may be obtained by addition of copper formate to pulp in the beater and subjecting the resulting paper to heating according to the invention.

The following examples will serve to illustrate some embodiments of the invention:

Example 1 Southern pine two-by-fours were impregnated with an aqueou solution of copper formate by the full-cell process. They were placed in the cell and subjected to an initial vacuum period of thirty minutes at a vacuum of 28-29 inches of mercury. The cell was then filled with a 2% aqueous solution of copper formate while maintaining the vacuum. After the cell was filled with the solution, a pressure of 180 p. s. i, gauge was maintained on the contents for three hours and then the pressure was released and the copper formate solution was withdrawn. The contents of the cell were then subjected to a final vacuum period of fifteen minutes at a vacuum of 27 inches of mercury. The vacuum was then released and steam at 121 C. p. s. i. gauge pressure) was introduced and maintained in the cell for a period of four hours. This treatment resulted in a copper retention in the sapwood of 31% based on the dry weight of the wood. The lumber so treated showed marked resistance to agents of decay associated with the soil and to marine organisms.

Example II A copper formatc solution was prepared by adding to a 2% solution of formic acid in water a stoichiornetric neutralizing excess of basic cupric carbonate with agitation. The solution was filtered to remove the excess cupric carbonate. Cotton duck was then impregnated with the solution and pa sed through rollers adjusted to give approximately a 70% pickup by the fabric. The impregnated fabric was then air dried and placed in an autoclave where it was subjected to steam under 15 p. s. i. guagc for thirty minutes. At the end of the autoclaving, the original green color had changed to a tan. The fabric contained 0.82% copper based on the dry weight of the fabric. subjection of the thus treated fabric to a rot resistance test with C. globosum in a suitable culture medium for fourteen days at a temperature of about C. and a relative humidity of about 93% resulted in no decrease in strength wherea an untreated sample of the duck subjected to the same conditions totally disintegrated during that period, showing no residual strength.

Similar results were obtained when treated and untreated duck subjected to an accelerated simulated weathering involving alternate wetting and drying and exposure to ultraviolet light was then subjected to the C. globosum test. Similarly, subjection of untreated duck to the action of Aspergillus niger resulted in heavy growth of the organism on the duck while there was no growth on the treated duck. Untreated duck subjected to a soil burial test showed no residual strength after three weeks c posurc, whereas the treated duck showed residual rgth after nine weeks exposure to soil under identical conditions. Similar results may be obtained by treating pre-treated cotton fabrics, as for example kicr-boiled and mercerized fabrics.

Example llI Eighteen ounce cotton duel: was treated as described in the preceding example except that the copper formats solution with which the duck was treated contained only half the amount of copper formate that was in the ing solution described in the preceding example. The resulting cotton duck performed similarly to the product of the preceding example save that its residual strength after nine and fourteen weeks burial in soil was somewhat lower.

Err/triple 1V An eighteen ounce cotton duck was treated with a solution prepared by adding a neutralizing excess of basic cupric carbonate to a 4% solution of formic acid in water and filtering off the excess basic cupric carbonate. The impregnated fabric was then passed through rollers adjusted to give a pickup of 70% of water on untreated cotton duck. The duck was then air dried and subjected to steam at 15 p. s. i. gauge for thirty minutes. The resulting cotton duck showed marked immunity to agents of decay.

Example V Sisal twine was treated with a solution of cupric formate and autoclaved for one-half hour resulting in a copper pickup of l.26%. Sisal thus treated showed far greater resistance to destruction by C. globnsmn than did untreated sisal from the same lot.

Exmnple V I Cotton fabric was treated with a cupric formate solution to give a copper pickup of about 0.8%. One portion of the impregnated air dried fabric was heated to C. in dry air at atmospheric pressure for fifteen minutes and another portion was heated to l20 C. in nitrogen at atmospheric pressure for an equal time. Both of the treated materials were immune to the action of C, globosum.

Example VII Wood chips were impregnated with an aqueous copper formate solution to give a pickup of 1% copper based on the weight of the treated wood. The chips were air dried and then autoclaved with steam at 15 p. s. i. pressure for one hour. The chips were washed in water until neutral to pH paper. The chips so treated and similar untreated chips were utilized in the manufacture of paper by the sulfate (lcraft) process and by the neutral sultite process. The ltraft paper made from treated chips contained 0.89% copper and the sulfitc paper made from treated chips contained 0.84% copper. Both of these papers showed complete resistance to C. ,ulobosum, while each of the papers made from untreated chips showed no resistance to the growth of that organism.

Example VIII Aqueous copper formate was added to sulfate process pulp in a beater to give a pickup of 1% copper based on the dry solids weight of the pulp. Paper was then made from the treated pulp. One portion of the resulting paper was heated at 121 C. for thirty minutes in 9 an autoclave and the remaining portion was not so heated. Upon subjection to C. globosum, the paper which had not been subjected to the heat treatment allowed heavy growth of the organism of the same character as untreated paper. By contrast, the paper which was subjected to the heat treatment permitted no growth of the organism. Similar results were obtained by treating neutral sulfite pulp in the beater.

This application is substituted for and is a continuation-in-part or" my co-oending application Serial No. 158,609, filed April 27, 1950, now abandoned, which in turn is a continuation-in-part of and was co-pending with my application Serial No. 687,695, filed August 1, 1946, now abandoned.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A process for increasing the immunity of cellulosic materials to organic agents of decay by provision therein of copper in chemically bound relation with cellulose molecules of said materials which comprises incorporating cupric formate in cellulosic material, decomposing said cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus incorporated in said materials by heating the cellulosic material containing said incorporated cupric formate to a temperature above about 100 C. but below temperatures that are capable of deleteriously affecting the cellulosic material.

2. The product produced by the process of claim 1.

3. A process for increasing the immunity of cellulosic materials to organic agents of decay by provision therein of copper in chemically bound relation with cellulose molecules of said materials which comprises impregnating cellulosic material with a solution containing cupric formate and decomposing said impregnated cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with said material by heating the impregnated cellulosic material to a temperature between about 100 C. and about 200 C.

4. A process for increasing the immunity of cellulosic materials to organic agents of decay by provision therein of copper in chemically bound relation with cellulose molecules of said materials which comprises impregnating cellulosic material with an aqueous solution containing cupric formate and decomposing said impregnated cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with said materials by heating the impregnated cellulosic material to a temperature between about 100 C. and about 200 C.

5. The process of claim 4 characterized by the heat ing being accomplished in the presence of steam.

6. A process for increasing the immunity of cellulosic materials to organic agents of decay by provision therein of copper in chemically bound relation with cellulose molecules of said materials which comprises impregnating cellulosic material with an aqueous solution containing cupric formate and decomposing said impregnated cupric 'formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with said materials by heating the impregnated cellulosic material to a temperature between about 100 C. and about 125 C.

7. A process for increasing the immunity of cotton to organic agents of decay by provision therein of copper in chemically bound relation with cellulose molecules of said cotton which comprises incorporating cupric formate in cotton, decomposing said cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus incorporated in said cotton by heating the cotton containing said incorporated cupric formate to a temperatureabove about 100 C. but below temperatures that are capable of deleteriously affecting the cotton.

8. The product produced by the. process of claim '7.

9. A process for increasing the immunity of cotton to organic agents of decay by provision therein of copper in chemically bound relation with cellulose molecules of said cotton which comprises impregnating cotton with a solution containing cupric formate and decomposing said impregnated cupric formate and efiecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with said cotton by heating the impregnated cotton to a temperature between about C. and about 200 C.

10. A process for increasing the immunity of cotton to organic agents of decay by incorporation therein of copper in chemically bound relation with cellulose molecules of said cotton which comprises impregnating cotton with an aqueous solution containing cupric formate and decomposing said impregnated cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with said cotton by heating the impregnated cotton to a temperature between about 100 C. and about 200 C.

11. The process as set forth in claim 10 characterized by the heating being efiected in the presence of steam.

12. A process for increasing the immunity of cotton to organic agents of decay by incorporation therein of copper in chemically bound relation with cellulose molecules of said cotton which comprises impregnating cotton with an aqueous solution containing cupric formate and decomposing said impregnated cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with said cotton by heating the impregnated cotton to a temperature between about 100 C. and about C.

13. A process for increasing the immunity of cellulosic materials to organic agents of decay by incorporation therein of copper in chemically bound relation with cellulose molecules of said materials which comprises impregnating cellulosic material with an aqueous solution containing cupric formate, drying said impregnated material and decomposing said impregnated cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with said materials by heating the impregnated, dried cellulosic material to a temperature between about 100 and about C.

14. A process for increasing the immunity of cotton to organic agents of decay by incorporation therein of copper in chemically bound relation with cellulose molecules of said cotton which comprises impregnating cotton with an aqueous solution containing cupric formate, drying said impregnated cotton, and decomposing said cupric formate and effecting chemicalcombination between said cellulose molecules and a substantial portion of the copper thus introduced into contact with said cotton by heating the impregnated dry cotton to a temperature between 100 and 150 C.

15. A process for increasing the immunity of cotton to organic agents of decay by incorporation therein of copper in chemically bound relation with cellulose molecules of said cotton which comprises impregnating cotton with an aqueous solution containing cupric formate and decomposing said impregnated cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into contact with said cotton by heating the impregnated cotton to' a temperature between about 100 C. and 125 C. in the presence of steam under pressure.

16. A process for increasing the immunity of cellulosic materials to organic agents of decay by incorporation therein of potentiating amounts of copper in chemically aqueous solution containing cupric formate, retaining in said cellulosic material an amount of cupric formate equal to a retained copper value of 0.01% to 2% based on the dry weight of the cellulosic material treated, and converting at least a portion of said retained cupric formate to copper firmly chemically bound to said cellulose molecules, the said converted portion being equivalent to at least 0.005% copper on the dry weight of said cellulosic material treated, by heating the impregnated cellusosic material to a temperature between about 100 and 200 C.

17. A process for increasing the immunity of cellulosic materials to organic agents of decay by incorporation therein of potentiating amount of copper in chemically bound relation with cellulose molecules of said materials which comprises impregnating cellulosie material with an aqueous solution containing cupric forinate, retaining in said cellulosic material an amount of cupric fortnate equal to a retained copper value of 0.1% to 1% based on the dry weight of the cellulosic material treated, converting at least a portion of said retained cupric formate to copper firmly chemically bound to said cellulose molecules, the said converted portion being equivalent to from 0.05% to 0.4% copper based on the dry weight of said cellulosic material treated, by heating the impregnated cellulosic material to a temperature between about 100 C. and 200 C.

18. A process for increasing the immunity of cotton materials to organic agents of decay by incorporation therein of potentiating amount of copper in chemically bound relation with cellulose molecules of said cotton which comprises impregnating cotton with an aqueous solution containing cupric formate, retaining in said cotton an amount of cupric formate equal to a retained cop per value of 0.l%-2% based on the dry weight of the cotton treated, converting at least a portion of said retained cupric formate to copper chemically bound to said cellulose molecules, the said chemically bound copper portion comprising at least 0.05% of the dry weight of said cotton treated, by heating the impregnated cotton to a temperature between about 100 and 150 C.

19. A process for increasing the immunity of cotton to organic agents of decay by incorporation therein of potentiating amount of copper in chemically bound relation with cellulose molecules of said cotton which comprises impregnating cotton with an aqueous solution containing cupric formate, retaining in said cotton an amount of cupric formate equal to a retained copper value of 0.1% to 1% based on the dry weight of the cotton treated, converting at least a portion of said retained cupric formate to copper firmly chemically bound to said cellulose molecules, the said converted portion being equivalent to from 0.05% to 0.4% copper based on the dry weight of said cotton treated, by heating the impregnated cotton to a temperature between about 100 C. and 200 C.

20. In the art of preserving wood by provision therein of copper in chemically bound relation with cellulose molecules of said wood, the process which comprises incorporating cupric formate in wood, decomposing said cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with the wood by heating the cupric formate-containing wood to a temperature above about 100 C. but below temperatures that are capable of dcleteriously affecting the wood.

21. The product produced by the process of claim 20.

22. In the art of preserving wood, a. process for incorporating in said wood copper in chemically bound relation with cellulose molecules of said wood which comprises impregnating wood with a solution of cupric formate, decomposing said impregnated cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper 12 thus impregnated into said wood by heating the impregnated wood to a temperature between about C. and 200 C. in the presence of steam under pressure.

23. In the art of preserving wood, a process for incorporating in said wood copper in chemically bound rela tion with cellulose molecules of said wood which comprises impregnating wood with an aqueous solution containing from about 1% to about 12% of cupric formate, decomposing said impregnated cupric formate and effecting chemical combination between said cellulose molecules and a substantial portion of the copper thus introduced into intimate contact with said wood by heating the impregnated wood to a temperature between about 100 C. and C.

24. In the art of preserving wood, the step of impregnating the wood with an aqueous solution containing from about 1% to about 12% cupric formate, decomposing said impregnated cupric formate and effecting chemical combination between cellulose molecules in said wood and a substantial portion of the impregnated copper by heating the impregnated wood to a temperature between about 100 C. and about C.

25. In the art of preserving wood, the steps of vacuum impregnating the wood with an aqueous solution containing from about 1.5% to about 4% cupric formate and reacting the said cupric formate with cellulose contained in said wood to provide copper in chemically bound relation with cellulose molecules of said wood by heating the impregnated wood by means of steam to a temperature between about 100 C. and about 125 C.

26. A method for increasing the immunity of wood to organic agents of decay by incorporation therein of copper in chemically bound relation with cellulose molecule-s of said wood which comprises subjecting the wood to partial vacuum; then contacting the wood with an aqueous solution of cupric formate under pressure; withdrawing excess cupric formate solution; and decomposing cupric formate and effecting chemical combination between cellulose molecules of said wood and a substantial portion of the copper thus introduced into intimate contact with said wood by heating the solution-treated wood sutficiently to raise the temperature of the wood to at least about 100 C. but below temperatures that are capable of deleteriously affecting the wood.

27. in the art of increasing the immunity of cellulosic paper to organic agents of decay, a process which comprises incorporating into the cellulose base of said paper copper in chemically bound relation with cellulose molecules of said cellulose base by treating said cellulose base with a solution containing cupric formate and decomposing cupric formate in the treated base and effecting chemical combination between cellulose molecules in said base and a substantial portion of copper by heating the treated base to a temperature between about 100 and 150 C.

28. The product produced by the process of claim 27.

29. The method of claim 27 characterized by the impregnation and heating of said treated base being effected prior to the pulping of said cellulose base.

30. The process or claim 27 characterized by the impregnation of the cellulose base being effected in the beater stage and the heating of said treated base being effected by heating formed paper.

Irish Text. I, 1941, 7, No. 3, 16-17. Textile J. Australia, 1941, 16, 237. 

1. A PROCESS FOR INCREASING THE IMMUNITY OF CELLULOSIC MATERIALS TO ORGANIC AGENTS OF DECAY BY PROVISION THEREIN OF COPPER INC HEMICALLY BOUND RELATION WITH CELLULOSE MOLECULES OF SAID MATERIALS WHICH COMPRISES INCORPORATING CUPRIC FORMATE IN CELLULOSIC MATERIAL, DECOMPOSING SAID CUPRIC FORMATE AND EFFECTING CHEMICAL COMBINATION BE TWEEN SAID CELLULOSE MOLECULES AND A SUBSTANTIAL PORTION OF THE COPPER THUS INCORPORATED IN SAID MATERIALS BY HEATING THE CELLULOSIC MATERIAL CONTAINING SAID INCORPORATED CUPRIC FORMATE TO A TEMPERATURE ABOVE ABOUT 100* C. BUT BELOW TEMPERATURES THAT ARE CAPABLE OF DELETERIOUSLY AFFECTING THE CELLULOSIC MATERIAL. 